The overall objectives of this project are 1) to investigate the control of liver growth and function, 2) to identify hormones and other factors involved in the regulation of hepatic metabolism, and 3) to determine the mechanism of action of these regulatory agents. Several areas of research are currently being pursued. The effects of growth hormone, insulin and fasting on hepatic amino acid transport are being studied in intact rats, isolated perfused livers and isolated hepatocytes. The level of activity and the rates of synthesis and degradation of specific liver proteins including ornithine decarboxylase, S-adenosylmethionine decarboxylase, phenylalanine hydroxylase and albumin are being determined in rat livers perfused in the presence and absence of hormones such as insulin, growth hormone, and glucocorticoids and substrates such as amino acids and fatty acids. A factor that promotes the growth of viral-transformed fibroblasts and that is released by perfused rat liver is being further characterized and the control of its release studied.